1. Field of the Invention
This invention relates to cyanoacrylate adhesive compositions which are improved in peel strength by incorporation of certain organic fillers.
2. Description of the Prior Art
Liquid cyanoacrylate compositions have long been known in the art as excellent adhesives. One of their primary shortcomings, however, has been their relatively low peel strength.
A variety of fillers has been incorporated into cyanoacrylate adhesive compositions to bring about certain changes in properties. U.S. Pat. No 2,794,788 teaches thickening of cyanoacrylate adhesives by dissolving therein quantities of polymeric alkyl cyanoacrylates, as well as other compounds including polyacrylates, methacrylates and cellulose esters such as acetate, propionate and butyrate.
U.S. Pat. No. 3,836,377 notes among the additional known thickeners polyvinyl ethers such as polyvinylmethyl ether. U.S. Pat. No. 3,692,752 discloses thickened cyanoacrylate solutions containing certain polyether acrylates/methacrylates, acrylic/methacrylic esters of bis(hydroxyalkyl) phosphonic acid derivatives, and acrylic/methacrylic esters of tris(hydroxyalkyl) cyanuric acid derivatives.
The preceding references relate to thickened homogeneous solutions containing organic compounds as thickeners. Various inorganic materials have also been proposed as fillers, which also have the effect of thickening the composition. Thus, U.S. Pat. No. 3,663,501 teaches preparation of a dental cement containing inert, finely-divided solids such as fused silica, quartz and alumina. Similarly, U.S. Pat. No. 3,607,542 teaches the preparation of a water-resistant cyanoacrylate paste containing insoluble, inert fillers such as salts of calcium, titanium, zinc, tin, aluminum, iron and copper, among others.
None of the above references relates to specific improvement of peel strength, nor to the use of the specific organic additives of this invention. Two of the additives of this invention are known, however, as impact-strength improving for certain rigid plastics such as rigid PVC. These additives are acrylonitrile-butadiene-styrene (ABS) and methacrylate-butadiene-styrene (MBS) block or graft terpolymers. These materials are not known as peel strength modifiers, nor are they known for any use in room-temperature-curable adhesive systems.